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February 18, 2008

Fast Foods, Exercise and Your Liver

We have known for many years that insulin resistance can cause non-alcoholic fatty liver disease (NAFLD). Now a new study published in the journal Gut reports that too much fast food and too little exercise can harm the liver in a matter of weeks.

In an experiment looking a lot like Morgan Spurlock’sSuper Size Me, Swedish researchers selected 18 thin, healthy volunteers - 12 men and 6 women - to attempt a 5 to 15% body weight increase by eating at least two fast-food-based meals per day for four weeks. The participants in this intervention group also restricted their level of physical activity to no more than 5000 steps a day. A comparison group, matched for age and sex, ate a normal diet and maintained normal exercise levels.

The plan was to see if doubling calorific intake and increasing total body weight had any impact on participant's liver health.

Changes in major liver enzymes, such as alanine aminotransferase (ALT), and in hepatic triglyceride content (HTGC) were used to indicate liver damage. Abnormally high ALT levels are frequently seen in people who consume a lot of alcohol or who have been infected with the hepatitis C virus. HTGC measures fatty acid levels in the liver; too much fat in the liver leads to a condition called fatty liver disease.

At the end of the four weeks, the researchers found that:

Fast-food consumers had put on an average of 6.5 kg (14.3 lbs.)

Five participants increased their weight by 15%

One person gained 12 kg (26.4 lbs.) in two weeks

Sharp increases in ALT occurred after just one week on the fast food diet

The average ALT level increased four-fold from 22 U/l to of 97 U/l over the 4 weeks

ALT rose to liver damage levels in 11 participants

No changes were seen in levels in the comparison group

The increases in ALT levels were linked to weight gain and increased sugar and carbohydrate intake. One subject developed fatty liver disease, and there was a large rise in liver cell fat content in the other participants

Although nobody should be surprised that gorging on junk food and becoming a couch potato is bad for the body, the speed and extent of the liver damage is alarming.